1. Technical Field
Example embodiments of the present invention relate to an interpolation filter, and more specifically to an interpolation filter based on time assignment algorithm which can process data having various input/output data rates.
2. Related Art
One of main blocks used in a mobile communication system is a filter. Especially, an interpolation filter is used for changing a sampling rate of outputs while maintaining a property of signal to be transmitted. The basic components for the interpolation filter include a delaying part, a multiplication and a summation part. Among the components, the multiplication part occupies the largest area in the interpolation filter. That is, the multiplication part is a main cause of increasing a cost of hardware for the interpolation filter.
In order to reduce cost of the hardware constituting the filter, it is an important issue to decrease the number of multipliers used for the multiplication part. Therefore, various interpolation filter structures (for example, a poly-phase transversal structure, a cascade structure, etc.) have been proposed in order to reduce the number of multipliers.
The poly-phase transversal structure is a structure in which a multiplier is shared by changing filter coefficients applied to the multiplier according to time proportionally to interpolation up-sampling ratio. If the poly-phase transversal structure is used, although there is an advantage of reducing the number of multipliers proportionally to a ratio of up-sampling, there may be a problem of increasing memory required for storing the filter coefficients due to the increased number of filter coefficients when the ratio of up-sampling is very large.
Meanwhile, the cascade structure is a structure in which multiple interpolation filters are used by dividing up-sampling ratio into small multiple up-sampling ratios. According to the cascade structure, there may be advantages in reducing the number of multipliers and filter coefficients. However, there is a problem that the number of multiplies which can be reduced is restricted according to the cascade structure.